Steady state combustors are used in various applications from gas turbine engines, various furnaces and heaters, and more recently, diesel engine exhaust after-treatment. These combustors maintain a constant or steady state flame in order to release energy from a fuel.
Steady state combustors can operate off of gaseous, liquid, or in some cases, solid fuels. Liquid fuel operation has several challenges for steady state combustors. In order to operate at maximum efficiencies and stabilities, The liquid fuel must be atomized with a nozzle into very small droplets. The atomization process allows the fuel to vaporize in as short a time as possible after leaving the nozzle. The fuel vapor must also mix with an oxidizer, such as air, as quickly as possible.
Methods have been developed to enhance fuel. Air-blast and air-assist nozzles are employed for the atomization of liquid fuels into minute droplets in an air atmosphere suitable for rapid and efficient combustion. These nozzles have very good atomization characteristics across very wide fuel flow rates, referred to as a good turn-down ratio. The airflow through the nozzle can also be directed in such a way that it can be used for atomization of the fuel liquid, vaporization of the liquid fuel droplets, mixing of the fuel vapor, and combustion of the fuel and oxidizer mixture. Because of the importance of the nozzle airflows in the fuel preparation and combustion process, the aerodynamics of the nozzle can be a critical factor of the nozzle design. Historically, this has produced nozzles that have had to incorporate expensive and complex geometries in order to meet the aerodynamic and fuel pattern requirements of the combustor.